Technologies have been known that perform various drive supports such as prevention of going out of a lane using white lines captured by a camera on a vehicle. When white lines are not detected, or to improve detection precision of the white lines, there are cases where a curbstone or a sidewalk step is detected as a clue of white lines (see, for example, Patent Document 1). Patent Document 1 discloses an image recognition device that detects a curbstone, by using an increasing or decreasing change of the length of a side surface part of the curbstone, and an increasing or decreasing change of the length of a parallel part parallel to a road surface, depending on the distance from a camera.
However, the image recognition device disclosed in Patent Document 1 has a problem in that it is difficult to detect a curbstone at a comparatively distant place from the vehicle.
FIG. 26(a) is an example of a diagram illustrating a conventional captured image of a far-off curbstone and a neighboring curbstone, and FIG. 26(b) is an example of a schematic view of the photograph of FIG. 26(a). There is a curbstone on the left side of a vehicle, and the side wall part of the curbstone is captured in the shade. As the lengths of the side surface part and the parallel part parallel to the road surface look shorter when going further, it is difficult for a detection method described in Patent Document 1 to detect a far-off curbstone.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2007-018037